knex-to-csv

knex-to-csv

Adds the .toStreamCSV() function to Knex's query builder to stream rows from Knex in CSV format to a writable stream.

Install

$ npm i knex-to-csv --save

Setup

Import and call the attachToStreamCSV() function after importing Knex:

const knex = require('knex');
const {attachToStreamCSV} = require('knex-to-csv');
attachToStreamCSV();

Usage

Export Knex rows to a CSV file:

const fs = require('fs')

csvWriter = fs.createWriteStream('/tmp/export.csv');

await knex.select().from('users').toStreamCSV(csvWriter)

// or with promise
knex.select().from('users').toStreamCSV(csvWriter)
    .then(() => {
        console.log('CSV exported successfully!');
    })
    .catch(e => {
        console.log(e);
    })

Specify CSV options and export Knex result rows to a CSV file:

const fs = require('fs')

csvWriter = fs.createWriteStream('/tmp/export.csv');

await knex.select().from('users').toStreamCSV(csvWriter, {csv: {separator: '|', newline: '\n'}})

Note

From Knex.js documentation:

If you wish to use streams with PostgreSQL, you must also install the pg-query-stream module. If you wish to use streams with the pgnative dialect, please be aware that the results will not be streamed as they are received, but rather streamed after the entire result set has returned. On an HTTP server, make sure to manually close your streams if a request is aborted.

API

toStreamCSV(writableStream, options?): Promise<number>

writableStream

Any writable stream or Duplex stream that implements the stream.Writable class such as fs write streams, http ServerResponse, TCP sockets, Zlib streams, etc.

options

Type: object

Default: {}

Keys: path, csv

• path

  Type: any

  Default: undefined

  A path for JSONStream.parse

• csv

  Type: object

  Default: {separator: ',', newline: '\n', headers: undefined, sendHeaders: true}

  Options to pass to csv-write-stream

License

MIT

Acknowledgements

This library was inspired from the following libraries:

• knex-on-duplicate-update
• json-to-csv-stream